A Fourier Transform Infrared Study on the Structure of Water Solubilized by Reverse Aggregates of Sodium and Magnesium Bis(2-ethylhexyl)sulfosuccinates in Organic Solvents

Novaki, Luzia P.; Seoud, Omar A. El

doi:10.1006/jcis.1998.5415

Cited by 33 publications

(42 citation statements)

References 66 publications

(6 reference statements)

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“…77 The absorption spectra of the OD stretch of HOD in water nanopools in reverse micelles are consistent with water properties that vary continuously within a micelle for a given w 0 . 36 However, the spectrum could also be composed of distinct species that have such broad and overlapping spectra that they are not resolved. The vibrational echo experiments presented below suggest that, at least for very small reverse micelles, water molecules exist with dynamical properties that vary with wavelength.…”

Section: Resultsmentioning

confidence: 99%

Dynamics of Nanoscopic Water: Vibrational Echo and Infrared Pump−Probe Studies of Reverse Micelles

2005

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The dynamics of water in nanoscopic pools 1.7-4.0 nm in diameter in AOT reverse micelles were studied with ultrafast infrared spectrally resolved stimulated vibrational echo and pump-probe spectroscopies. The experiments were conducted on the OD hydroxyl stretch of low-concentration HOD in the H 2 O, providing a direct examination of the hydrogen-bond network dynamics. Pump-probe experiments show that the vibrational lifetime of the OD stretch mode increases as the size of the reverse micelle decreases. These experiments are also sensitive to hydrogen-bond dissociation and reformation dynamics, which are observed to change with reverse micelle size. Spectrally resolved vibrational echo data were obtained at several frequencies. The vibrational echo data are compared to data taken on bulk water and on a 6 M NaCl solution, which is used to examine the role of ionic strength on the water dynamics in reverse micelles. Two types of vibrational echo measurements are presented: the vibrational echo decays and the vibrational echo peak shifts. As the water nanopool size decreases, the vibrational echo decays become slower. Even the largest nanopool (4 nm, ∼1000 water molecules) has dynamics that are substantially slower than bulk water. It is demonstrated that the slow dynamics in the reverse micelle water nanopools are a result of confinement rather than ionic strength. The data are fit using time-dependent diagrammatic perturbation theory to obtain the frequency-frequency correlation function (FFCF) for each reverse micelle. The results are compared to the FFCF of water and show that the largest differences are in the slowest time scale dynamics. In bulk water, the slowest time scale dynamics are caused by hydrogen-bond network equilibration, i.e., the making and breaking of hydrogen bonds. For the smallest nanopools, the longest time scale component of the water dynamics is ∼10 times longer than the dynamics in bulk water. The vibrational echo data for the smallest reverse micelle displays a dependence on the detection wavelength, which may indicate that multiple ensembles of water molecules are being observed.

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Section: Resultsmentioning

confidence: 99%

Dynamics of Nanoscopic Water: Vibrational Echo and Infrared Pump−Probe Studies of Reverse Micelles

2005

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“…Therefore, micellar size may affect the local aqueous environment, which in turn may affect the catalytic properties of the enzyme in that environment (Bru et al 1989). Other studies suggest that water has a uniform structure within the interior of the reverse micelle (Novaki and El Seoud 1998). Evidently, the uncertainty about the structure of water within reverse micelles hinders the interpretation of results (Faeder and Ladanyi 2000).…”

Section: Introductionmentioning

confidence: 91%

Reverse micelles in organic solvents: a medium for the biotechnological use of extreme halophilic enzymes at low salt concentration

Marhuenda-Egea

Piera-Velázquez

Cadenas

et al. 2002

Archaea

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Summary Alkaline p-nitrophenylphosphate phosphatase ( pNPPase) from the halophilic archaeobacterium Halobacterium salinarum (previously halobium) was solubilized at low salt concentration in reverse micelles of hexadecyltrimethylammoniumbromide in cyclohexane with 1-butanol as cosurfactant. The enzyme maintained its catalytic properties under these conditions. The thermodynamic "solvation-stabilization hypothesis" has been used to explain the bell-shaped dependence of pNPPase activity on the water content of reverse micelles, in terms of protein-solvent interactions. According to this model, the stability of the folded protein depends on a network of hydrated ions associated with acidic residues at the protein surface. At low salt concentration and low water content (the ratio of water concentration to surfactant concentration; w 0 ), the network of hydrated ions within the reverse micelles may involve the cationic heads of the surfactant. The bell-shaped profile of the relationship between enzyme activity and w 0 varied depending on the concentrations of NaCl and Mn 2+.

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“…Infrared spectroscopy (IR) is a noninvasive technique suitable for detecting hydrogen bonds and has often been employed to study the states of water solubilized in reverse micelles in many laboratories [7,8,[16][17][18][19][20][21][22][23][24][25][26]. The purposes of this paper is to reveal the states of water in the reversed micelles formed by C 12 -s-C 12 ·2Br in n-heptane by FT-IR techniques and to discuss the effects of the molecular structure of the gemini surfactant on the properties of water.…”

Section: Introductionmentioning

confidence: 99%

“…O-H stretching bands of water solubilized by the reverse micelles in the water/C 12 -2-C 12 ·2Br (0.1 M)/n-hexanol/n-heptane system (I), where from 1 to 7, W 0 (the mole ratio of water to surfactant) is10,12,15,18,20,22, and 25, respectively. Similar spectra for water/C 12 TABr (0.1 M)/n-hexanol/n-heptane system are shown in (II) for comparison, where from 1 to 6, W 0 is 10, 15, 20, 25, 30, and 35, respectively.…”

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confidence: 99%

Fourier transform infrared investigation on the state of water in reverse micelles of quaternary ammonium gemini surfactants C12-s-C12⋅2Br in n-heptane

Zhao¹,

Deng²,

Liu³

et al. 2007

Journal of Colloid and Interface Science

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A Fourier Transform Infrared Study on the Structure of Water Solubilized by Reverse Aggregates of Sodium and Magnesium Bis(2-ethylhexyl)sulfosuccinates in Organic Solvents

Cited by 33 publications

References 66 publications

Dynamics of Nanoscopic Water: Vibrational Echo and Infrared Pump−Probe Studies of Reverse Micelles

Dynamics of Nanoscopic Water: Vibrational Echo and Infrared Pump−Probe Studies of Reverse Micelles

Reverse micelles in organic solvents: a medium for the biotechnological use of extreme halophilic enzymes at low salt concentration

Fourier transform infrared investigation on the state of water in reverse micelles of quaternary ammonium gemini surfactants C12-s-C12⋅2Br in n-heptane

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